I compiled my own simple module for module load test, with gcc, successfully. But when i tried to load a module (.o file) with insmod cmd it has given following msg.
kernel-module version mismatch
syscall.o was compiled for kernel version 2.4.20
while this kernel is version 2.4.22-1.2115.nptl.

I have PCQLinux with kernel version 2.4.22-1.2115.nptl installed. I also tried including all headers from /ur/src/Linux-2.4.22-1.2115.nptl/include/linux dir. And I think the gcc compiler provided with this linux should generate the object code for the same version of kernel.
I really frustated, My project work is stopped due to this. Please help me out.

The compiler will not make the modules unless you tell it to do so with the commands 'make modules' and 'make modules_install'. From the info you've given, it sounds like you didn't complete the kernel compile process. Review the kernel compilation procedures: you should be able to pick up the thread from the point where you messed up.